Excess pressure relief system for tank

ABSTRACT

An excess pressure relief system for a tank ( 10 ) carried on a vehicle, which includes a relief valve ( 11 ) for relieving excess pressure in the tank ( 10 ); and a diffuser ( 12 ) provided on a discharge line ( 11   a ) downstream of the relief valve ( 11 ).

TECHNICAL FIELD

The present invention relates to a pressure relief system for relievingexcess pressure in a gas fuel tank, a hydrogen tank or the like by useof a relief valve.

BACKGROUND ART

A gas fuel tank mounted on a gas fuel vehicle is filled with liquefiedpetroleum gas (LPG) or compressed natural gas (CNG). A hydrogen tankmounted on a fuel cell vehicle is filled with liquefied hydrogen orhigh-pressure hydrogen gas.

Japanese Patent Application Laid-Open No. H7-195948 (published in 1995)discloses a structure for relieving excess pressure in a gas fuel tankby discharging gas from the gas fuel lank together with vaporized fuelto the outside by use of a relief valve when an internal pressure in thegas fuel tank is increased.

DISCLOSURE OF INVENTION

In the structure described above, when the relief valve opens to relieveexcess pressure in the gas fuel tank, the high pressure as therein jetsout of the relief valve together with the vaporized fuel, impinges onparts or equipment located in close front of an outlet of the reliefvalve in a jet direction, and affects the parts or equipment, causingaccelerated deterioration thereof.

The present invention was made in the light of the above problems. Anobject of the present invention is to provide an excess pressure reliefsystem for a tank carried on a vehicle, such as a gas fuel tank, ahydrogen tank or the like, which diffuses and attenuates a gas flowjetted out of a relief valve in order to prevent the gas flow fromaffecting parts or equipment in the vicinity of the relief valve.

An aspect of the present invention is an excess pressure relief systemfor a tank carried on a vehicle, comprising: a relief valve forrelieving excess pressure in the tank; and a diffuser provided on adischarge line downstream of the relief valve.

BRIEF DESCRIPTION OF DRAWINGS

The invention will now be described with reference to the accompanyingdrawings wherein:

FIG. 1 is a schematic of an excess pressure relief system according to afirst embodiment of the present invention;

FIG. 2 is an enlarged sectional view of a gas diffuser for use in theexcess pressure relief system of FIG. 1;

FIG. 3A is a perspective view of a first modification example of the gasdiffuser for use in the excess pressure relief system of FIG. 1, fromwhich an outer tube is omitted for clarity;

FIG. 3B is a longitudinal-sectional view of the gas diffuser of FIG. 3A,taken along a line IIIB-IIIB;

FIG. 3C is a cross-sectional view of the gas diffuser of FIG. 3A, takenalong a line IIIC-IIIC;

FIG. 4A is a perspective view of a second modification example of thegas diffuser for use in the excess pressure relief system of FIG. 1,from which an outer tube is omitted for clarity;

FIG. 4B is a longitudinal-sectional view of the gas diffuser of FIG. 4A,taken along a line IVB-IVB;

FIG. 4C is a cross-sectional view of the gas diffuser of FIG. 4A, takenalong a line IVC-IVC;

FIG. 5A is a perspective view of a third modification example of the gasdiffuser for use in the excess pressure relief system of FIG. 1, fromwhich an outer tube is omitted for clarity;

FIG. 5B is a longitudinal-sectional view of the gas diffuser of FIG. 5A,taken along a line VB-VB;

FIG. 5C is a cross-sectional view of the gas diffuser of FIG. 5A, takenalong a line VC-VC;

FIG. 6 is an enlarged sectional view of a gas diffuser for use in theexcess pressure relief system according to a second embodiment of thepresent invention;

FIG. 7 is a cross-sectional view of the gas diffuser of FIG. 6, takenalong a line VII-VII;

FIG. 8 is a schematic of an excess pressure relief system according to athird embodiment of the present invention;

FIG. 9 is an enlarged sectional view of a control valve for use in theexcess pressure relief system of FIG. 8;

FIG. 10 is an enlarged sectional view of a control valve for use in anexcess pressure relief system according to a fourth embodiment of thepresent invention;

FIG. 11 is a schematic of an excess pressure relief system according toa fifth embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be explained below withreference to the drawings, wherein like members are designated by likereference characters.

As shown in FIG. 1, an excess pressure relief system of a firstembodiment includes a fuel tank 10, a relief valve 11 and a gas diffuser12. The fuel tank 10 is filled with gas fuel such as LPG or CNG in a gasfuel vehicle, or with liquefied hydrogen or high-pressure hydrogen gasin a fuel cell vehicle. The relief valve 11 is provided on the fuel tank10 to relieve excess pressure in the tank 10. The gas diffuser 12 isprovided on a discharge line 11 a downstream of the relief valve 11, todiffuse and attenuate the discharged gas flow.

As shown in FIG. 2, the gas diffuser 12 includes an inner tube 20connected to the end of the discharge line 11 a, an outer tube 30provided coaxially with and radially outside the inner tube 20 leaving acolumnar space therebetween, and an intermediate diffuser member 40,arranged in the space between the inner tube 20 and the outer tube 30,for diffusing and moderating the discharged gas flow. The inner tube 20is formed to have a large number of through holes 21 on itscircumferential side face 20 a. The outer tube 30 is formed to be longerin an axial direction thereof than a part 22 of the inner tube 20 formedwith the through holes 21. The outer tube 30 extends further towarddistal and base ends thereof than the through hole part 22 in the axialdirection thereof. A large number of discharge holes 31 are formed allover an outer circumferential surface 30 a of the outer tube 30 from abase end thereof to a distal end thereof. The discharge holes 31 areformed larger in diameter in the vicinities of the base and distal endsthan in the axially mid portion of the outer tube 30.

At the distal ends of the inner and outer tubes 20 and 30, an end plate32 is provided to close the openings thereof, and on the base endthereof, another end plate 32 a is provided to close an opening of theouter tube 30, so that the gas discharged from the relief valve 11 flowsout of the through holes 21 of the inner tube 20 into the intermediatemember 40, passes through the intermediate member 40 and flows out ofthe discharge holes 31 of the outer tube 30 to the outside.

The intermediate member 40 is made of a material which allows the gasflow flowed out of the through holes 21 to pass therethrough and absorbskinetic energy of the gas flow.

As described above, in this excess pressure relief system for a fueltank of the first embodiment, the gas diffuser 12 is provided on thedischarge line 11 a downstream the relief valve 11. Therefore, when thegas in the fuel tank 10 is discharged together with the vaporized fuelfrom the relief valve 11, the discharged gas flow is diffused by the gasdiffuser 12, whereby the gas flow is attenuated to have the pressure andkinetic energy thereof reduced. It is thus eliminated that thedischarged gas impinges on parts or equipment (not shown) located closein front of an outlet of the relief valve 11 in a jet direction, thussuppressing influence on the parts or equipment.

The configuration of the gas diffuser 12 forces the discharged gas toflow out of the through holes 21 of the inner tube 20 thereof, passthrough the intermediate member 40, and be discharged to the outsidefrom the discharge holes 31 of the outer tube 30, thus, effectivelyreducing the pressure and kinetic energy of the discharged gas flow, andproviding enhanced attenuation efficiency of the gas flow.

FIGS. 3A to 3C, 4A to 4C and 5A to 5C show first to third modificationexamples of the gas diffuser of the first embodiment, respectively. Thesame members therein as those of the first embodiment are designated bythe same reference characters, and explanations thereof are omitted.

As shown in FIGS. 3A to 3C, in a gas diffuser 50 according to the firstmodification example, the intermediate member 40 is essentially composedof a perforated tubular member 52 arranged in the space between theinner and outer tubes 20 and 30 coaxially therewith. The perforatedtubular member 52 is made of a perforated stainless steel plate 51 overwhich a large number of through holes 51 a are formed. Each through hole51 a is set to have a diameter D1 of a size suitable fordiffusing/moderating the discharged gas flow from the inner tube 20.

Also in the first modification example, the inner tube 20 is formed tohave a large number of the through holes 21 on the side face 20 athereof, and the outer tube 30 is formed to have a large number of thedischarge holes 31 on the outer circumferential surface 30 a thereof,respectively, and the end plates 32 and 32 a are provided to close theopenings at the both ends of the outer tube 30 in the axial direction,as in the first embodiment previously described.

In this gas diffuser 50, since the intermediate member 40 is essentiallycomposed of the perforated tubular member 52, resistance to thedischarged gas passing through the gas diffuser 50 can be adjusted bychanging the diameters D1 of the through holes 51 a on the perforatedplate 51 and the number thereof. Moreover, since the perforated plate 51of the perforated tubular member 52 is made of a stainless steel plate,which has excellent heat resistance and corrosion resistance, durabilityof the perforated tubular member 52 is improved.

In a gas diffuser 60 according to the second modification example, asshown in FIGS. 4A to 4C, the intermediate member 40 is essentiallycomposed of metal wool 61 which is a mass of unwoven fine stainlesssteel threads, like a metal scourer.

The metal wool 61 is arranged to fill the space between the inner andouter tubes 20 and 30. Gas discharged from the through holes 21 of theinner tube 20 passes through the metal wool 61, and is discharged to theoutside from the discharge holes 31 of the outer tube 30.

Also in the second modification example, the end plates 32 and 32 a areprovided to close the openings at the both ends of the outer tube 30 inthe axial direction, as in the first embodiment previously described.

In this gas diffuser 60, since the intermediate member 40 is essentiallycomposed of the metal wool 61, resistance to the discharged gas passingthrough the gas diffuser 60 can be adjusted by changing the fillingdensity of the stainless steel threads in the space between the innerand outer tubes 20 and 30. Moreover, since the metal wool 61 is made ofstainless steel, which has excellent heat resistance and corrosionresistance, durability of the metal wool 61 is improved.

In a gas diffuser 70 according to the third modification example, asshown in FIGS. 5A to 5C, the intermediate member 40 is essentiallycomposed of a tubular net 72 arranged in the space between the inner andouter tubes 20 and 30 coaxially therewith. The tubular net 72 is arolled stainless steel net 71 having a mesh size # suitable fordiffusing/moderating a gas flow discharged from the inner tube 20.

Also in the third modification example, the inner tube 20 is formed tohave a large number of the through holes 21 on the side face 20 athereof, and the outer tube 30 is formed to have a large number of thedischarge holes 31 on the outer circumferential surface 30 a thereof,respectively, and the end plates 32 and 32 a are provided to close theopenings at the both ends of the outer tube 30 in the axial direction,as in the first embodiment previously described.

In this gas diffuser 70, since the intermediate member 40 is essentiallycomposed of the tubular net 72, resistance to the discharged gas passingthrough the gas diffuser 70 can be adjusted by changing the mesh size #of the stainless steel net 71. Moreover, since the net 71 of the tubularnet 72 is made of stainless steel, which has excellent heat resistanceand corrosion resistance, durability of the tubular net 72 is improved.

FIGS. 6 and 7 show a second embodiment of the present invention.Hereinafter, the same members in the second embodiment as those of thefirst embodiment are designated by the same reference characters, andexplanations thereof are omitted.

A gas diffuser 80 of the second embodiment is a jet reverser including aplanar reverser plate 81 which is located in front of a gas outlet 11 bof the discharge line 11 a downstream of the relief valve 11 (seeFIG. 1) in the jet direction and perpendicular to the jet direction, anda tubular cover wall 82 extending rearward (opposite to the jetdirection) from the peripheral edge of the reverser plate 81 coaxiallywith the gas outlet 11 b and surrounding the periphery of the gas outlet11 b. A flow of gas discharged from the outlet 11 b impinges on thereverser plate 81, and turns into a radial flow directed radiallyoutward, thereby being diffused. Thereafter, the flow of the gasimpinges on the inner surface of the cover wall 82, whereby the gas flowis further diffused/attenuated. Deflected by the cover wall 82, the gasflow is then converted into an axial flow directed rearward.

The gas diffuser 80 is formed into a can container shape having thereverser plate 81 as a bottom thereof, and the cover wall 82 as a sidewall thereof. It also has a top plate 83 opposing the reverser plate 81in parallel. The top plate 83 is formed to have on its central portion ahub 83 d provided with an attachment hole 83 a into which the dischargeline 11 a is inserted. Around the hub 83 d, a plurality of relativelylarge fan-shaped openings 83 b are formed on the top plate 83 atsubstantially equal intervals in a circumferential direction. Remaindersof the top plate 83 between the openings 83 b are radially extendingsupports 83 c which connect the cover wall 82 to the hub 83 d. The gasdiffuser 80 is fixed to the discharge line 11 a inserted into theattachment bole 83 a of the hub 83 d, with an appropriate space D2 leftbetween the reverser plate 81 and the gas outlet 11 b.

The gas flow jetted out of the gas outlet 11 b is converted into therearward axial flow by the reverser plate 81 and the cover wall 82, andis discharged from the fan-shaped openings 83 b.

In an excess pressure relief system of the second embodiment, thepressure and kinetic energy of the gas flow jetted out of the gas outlet11 b are reduced by impinging on the reverser plate 81. The gas flow isdiffused and expanded inside the cover wall 82 while being reversed bythe reverser plate 81. This expansion further reduces the pressure andkinetic energy of the gas flow. Thereafter, the gas flow turns into therear rearward flow opposite to the jet direction at the gas outlet 11 b,and is discharged to the outside from the fan-shaped openings 83 b ofthe top plate 83.

The distance from the gas outlet 11 b to the inner surface of thereverser plate 81, and the diameter D3 of the cover wall 82 are adjustedto have the pressure and flow rate of the gas flow discharged from therelief valve 11 attenuated effectively.

FIGS. 8 and 9 show a third embodiment of the present invention.Hereinafter, the same members in the third embodiment as those of thefirst and second embodiments are designated by the same referencecharacters, and explanations thereof are omitted.

In an excess pressure relief system of the third embodiment, there isprovided in the discharge line 11 a of the relief valve 11 provided onthe fuel tank 10, a control valve 90 which controls a discharge rate ofgas.

As shown in FIG. 9, the control valve 90 includes a valve element 91which opens/closes the gas outlet 11 b, and a spring 92 which generatesforce to push the valve element 91 in a valve closing direction (towardthe left in the drawing). The control valve 90 is opened when a pressureof the gas discharged from the relief valve 11 in the discharge line 11a becomes higher than a valve cracking pressure of the control valve 90,which is determined by a force of the spring 92, and then the gas isdischarged from an outlet 93.

In the excess pressure relief system of the third embodiment, the valve90 starts opening when the pressure of the gas jetted out of the reliefvalve 11 reaches the valve cracking pressure of the control valve 90,and gradually increases its opening, making the gas discharge rategentle and slow. The rush of the high pressure gas discharge is thusprevented, suppressing the influence on the parts or equipment in thevicinity of the gas outlet 11 b.

FIG. 10 shows a fourth embodiment of the present invention. Hereinafter,the same members in the fourth embodiment as those of the thirdembodiment are designated by the same reference characters, andexplanations thereof are omitted.

A control valve 100 of the fourth embodiment includes a valve element101 which opens/closes the gas outlet 11 b, a spring 104 which generatesa force to push the valve element 101 in a valve closing direction(toward the right in the drawing), a solenoid 102 which drives thisvalve element 101 to open/close, and a controller 103 which sendsexcitation/non-excitation signals to the solenoid 102 in a controlledduty ratio.

The valve element 101 is pressed by the spring 104 in the valve closingdirection, and maintained in its closed state when the solenoid 102 isnot excited, and opened by the excitation of the solenoid 102. The dutyratio of the excitation/non-excitation signals to the solenoid 102 iscontrolled by Pulse Width Modulation (PWM) of the controller 103, andthus the discharge rate of the gas from the control valve 100 isregulated.

In an excess pressure relief system of the fourth embodiment, thecontroller 103 performs PWM to control the duty ratio of theexcitation/non-excitation signals to the solenoid 102 depending on themonitored pressure, temperature and the like inside the fuel tank 10.Therefore, the discharge rate of the gas can be actively and preciselycontrolled, providing optimum attenuation of the gas flow.

FIG. 11 shows a fifth embodiment of the present invention. Hereinafter,the same members in the fifth embodiment as those of the first to thirdembodiments are designated by the same reference characters, andexplanations thereof are omitted.

An excess pressure relief system of the fifth embodiment is providedwith the control valve 90 on the discharge line 11 a of the relief valve11, which controls the gas discharge rate, and the gas diffuser 12connected to the outlet 93 of the control valve 90, which attenuates anddiffuses the discharged gas flow.

The control valve 90 and the gas diffuser 12 have the sameconfigurations as those of the third and first embodiments,respectively.

The excess pressure relief system of the fifth embodiment is providedwith an integrated function of those of the control valve 90, whichenhances the attenuation efficiency of the discharged gas flow, and thegas diffuser 12, which further diffuses the attenuated gas flow,efficiently preventing the influence on the parts or equipment close infront of the relief valve 11 in the jet direction.

Moreover, in this embodiment, the control valve 100 of the fourthembodiment can bc used in place of the control valve 90 of the thirdembodiment. Further, in place of the gas diffuser 12 of the firstembodiment, the gas diffuser 50, 60 or 70 described in the first tothird modification examples or the gas diffuser 80 of the secondembodiment can be used.

The present disclosure relates to subject matter contained in JapanesePatent Application No. 2002-297212, filed on Oct. 10, 2002, thedisclosure of which is expressly incorporated herein by reference in itsentirety.

The preferred embodiments described herein are illustrative and notrestrictive, and the invention may be practiced or embodied in otherways without departing from the spirit or essential character thereof.The scope of the invention being indicated by the claims, and allvariations which come within the meaning of claims are intended to beembraced herein.

INDUSTRIAL APPLICABILITY

As described above, according to the excess pressure relief system for atank of the present invention, the relief valve 11, which discharges gasin the tank 10, is provided on the tank 10 such as a fuel tank or ahydrogen tank, and the gas diffuser 12 is provided in the discharge line11 a of the relief valve 11. Accordingly, a flow of gas jetting from therelief valve 11 can be attenuated, thus making it possible to preventthe discharged gas from affecting the parts or equipment in the vicinityof the relief valve 11.

1. An excess pressure relief system for a tank carried on a vehicle,comprising: a relief valve for relieving excess pressure in the tank;and a diffuser provided on a discharge line downstream of the reliefvalve.
 2. An excess pressure relief system for a tank carried on avehicle, comprising: a relief valve for relieving excess pressure in thetank; and a control valve for controlling gas discharge rate, providedon a discharge line downstream of the relief valve.
 3. An excesspressure relief system for a tank carried on a vehicle, comprising: arelief valve for relieving excess pressure in the tank; a control valvefor controlling gas discharge rate, provided on a discharge linedownstream of the relief valve; and a diffuser provided downstream ofthe control valve.
 4. The excess pressure relief system according toclaims 1 or 3, wherein the diffuser comprises: an inner perforatedmember connected to the discharge line, an outer perforated membersurrounding the inner member, and an intermediate diffuser memberarranged in a space between the inner and outer perforated members. 5.The excess pressure relief system according to claim 4, wherein thediffuser member is made of a perforated plate having holes ofpredetermined sizes.
 6. The excess pressure relief system according toclaim 4, wherein the diffuser member comprises a mass of unwoven metalthreads.
 7. The excess pressure relief system according to claim 4,wherein the diffuser member is made of a net of a predetermined meshsize.
 8. The excess pressure relief system according to claims 1 or 3,wherein the diffuser comprises: a deflector for deflecting gas flowdischarged from the relief valve, the deflector having a planer wallportion on which the discharged gas flow impinges and a tubular wallportion for turning the direction of the gas flow.
 9. The excesspressure relief system according to claims 2 or 3, wherein the controlvalve comprises: a valve element which opens/closes an outlet of therelief valve, and a resilient member which generates force to close thevalve element.
 10. The excess pressure relief system according to claims2 or 3, wherein the control valve comprises: a valve element whichopens/closes an outlet of the relief valve, a solenoid to drive thevalve element, and a controller for controlling duty ratio of thesolenoid.
 11. An excess pressure relief system for a tank carried on avehicle, comprising: a relief valve for relieving excess pressure in thetank; and diffusing means provided on a discharge line downstream of therelief valve.